Question

Which of the following causes ‘Type-I’ settling in a sedimentation tank?

• A. Agglomeration
• B. Compression
• C. Force of gravity
• D. Charge neutralization

Hint:

Type-I settling occurs when particles settle individually under the influence of gravity, with no interactions between particles.

Answer 1

The Correct Option is C

In a sedimentation tank, Type-I settling refers to the settling of discrete particles that do not interact with one another and settle under the influence of gravity.
This type of settling is the simplest and is driven solely by the force of gravity (C).
The particles are assumed to be uniform in size and shape, and they settle at a constant rate according to Stokes’ law.

- Agglomeration (A) refers to the clustering or sticking together of particles, which can occur in some types of settling but is not characteristic of Type-I settling.
- Compression (B) refers to the process that happens in the settling of flocs or larger particles, where the particles are pressed together as they settle. This is not related to Type-I settling.
- Charge neutralization (D) involves the interaction of particles with opposite charges, leading to aggregation or flocculation, which is relevant for Type-II or Type-III settling, but not for Type-I.

Therefore, the correct cause of Type-I settling is the force of gravity, which causes the particles to settle due to their size and density.

Final Answer:

\[ \boxed{(C)\; \text{Force of gravity}} \]